1. Plan for detecting flat workpieces Option 1: The wheeled phased array probe and CTS-2108PA phased array detector form a complete set of phased array C-scan rapid imaging detection system. The phased array detector works in the A+L+C detection module, using water as the coupling agent during detection. The probe is gently rolled, and the C-scan image is immediately presented, making it particularly suitable for C-scan detection of large area planar composite materials.     Option 2: A C-scan detection system is composed of a dual axis cable encoder, a high-resolution phased array probe, and a CTS-2108PA phased array detector (with a 2D-C scanning detection dedicated module). The cable encoder is fixed on the scanning workpiece during scanning, and magnetic or vacuum adsorption can be used to meet the requirements of different detection workpieces. When working, fix the wire clamps of the two cable encoders to the fixed positions of the scanning probe. The probe moves in any direction within the set detection range, making the scanning work as convenient as graffiti or painting. In addition to flat workpieces, it is also suitable for curved workpieces with small curvature.     Option 3: A simple scanner composed of a high-resolution phased array probe and a high-precision waterproof and dustproof encoder. Different wedges are designed according to different usage scenarios, which can meet various application scenarios. It can perform C-scan imaging detection on large composite materials and narrow space composite materials. The scanning equipment is simple, compact, and flexible to use. By customizing various types of wedges, Can meet different application scenarios.   2. Fillet workpiece detection plan The use of our company's CTS-2108PA phased array detector, supporting company curved linear array probes, and specialized wedges can perfectly solve the problem of fillet C-scan detection.  

1、 Methods for reducing internal stress 1. Hammering and forging - mechanical method When repairing long cracks and surfacing layers, it is necessary to continuously weld from one end to the other end. During the welding process, while the weld seam and surfacing layer are in a hot state, use a hammer to strike them, which can reduce the shrinkage of the weld seam and reduce internal stress. When striking, the effect is good when the welding repair metal temperature is 800 ℃. If the temperature drops, the tapping force also decreases. If the temperature is too low, it is not allowed to strike around 300 ℃ to avoid cracking. The principle of forging and smelting method is basically consistent with the above, but the difference is to heat all the welded parts before striking them. 2. Preheating and slow cooling - thermal method This method involves placing the workpiece to be welded in the furnace before welding repair, heating it to a certain temperature (100-600 ℃), and preventing rapid cooling of the heated workpiece during the welding process. The purpose of this treatment is to reduce the difference between the temperature of the welding repair section and the temperature of the base metal, thereby reducing internal stress. The method of slow cooling is to heat the welded workpiece to 600 ℃ and slowly cool it in an annealing furnace. 3. The method of 'breaking first and then standing' When welding cast iron parts with ordinary carbon steel electrodes, cracks are easily generated, and using cast iron electrodes is not economical. This article introduces a method of using carbon steel welding rods for welding, which is "first break and then stand": first cut along the weld seam with a small current, pay attention to only grooving without cutting through, and then weld while it is hot. Due to the elimination of local stress around the cracks during cutting, no new cracks will be generated, and the welding effect is very good. There are three methods to reduce internal stress during the welding process, as follows: welding of cracks in the cast iron pump casing. (1) Drill stop holes at both ends of the crack（ φ 10mm) to prevent further outward expansion of cracks during welding. (2) Use a manual polishing machine to make a groove at the crack location, with a width of 8-9mm at the top of the groove, slightly V-shaped, and a depth of 32mm (the wall thickness of this pump casing is 40mm), allowing for the welding of welding fluid. (3) Welding is manual welding, using φ 3.2mm special cast iron welding electrode, using a DC welding machine, reverse connected, with a current of 150A, is used for intermittent welding, that is, each welding seam is 15-20mm long, with a pause for a moment. In the gap between welding stops, when the welding melt solidifies and changes from a white hot state to a red hot state, use a small pointed hammer to hammer the electric welding seam. The hammer force should be light, the speed should be fast, and the number of times should be more, so as to reduce the thickness of the welding seam metal and extend it around, offset some welding seam shrinkage, and reduce welding stress. This can effectively improve the crack resistance of the welding seam metal (note that the small hammer head must be a circular arc with a radius of about 10mm). Wait until the welding pool cools down until the dark red color disappears before continuing welding. (4) For longer cracks, segmented welding repair is necessary to avoid cracking. The principle of segmentation is to first weld the section that can be freely retracted. If divided into three sections, the middle section should be welded first. When this section cools to the point where the dark red color disappears, the other section should be welded immediately, and then the last section should be welded. (5) Before welding, preheat the weld area and maintain insulation after welding to reduce the cooling rate. Preheating and insulation can not only improve the crack resistance of the weld metal, but also help reduce the hardness of the area near the fusion line. 2、 Methods to reduce and prevent deformation during welding 1. Preheating method Preheating the welded parts before welding can not only reduce internal stress, but also be a good method to reduce deformation. 2. Pre added anti deformation method The pre added reverse deformation method is based on the properties of the welded metal and estimates the direction and shrinkage of deformation after welding repair based on experience. Before welding repair, the workpiece is pre deformed using mechanical methods to make the deformation after welding repair exactly offset the pre deformation. 3. Water cooling method This method is to use cold water spray welding to prevent deformation by reducing the temperature of the base metal. Alternatively, the welding part can be immersed in a cold water bath to expose the part that needs to be welded, so that the temperature of the base metal does not rise, and therefore the welded part will not cause deformation. 4. Clamping method This method is to use a fixture with greater rigidity to fasten the welded part, preventing deformation of the welded part during welding. However, this method will residual internal stress inside the weldment, so it is mainly applied to the welding of low-carbon steel sheets with good plasticity. 5. Reasonable selection of welding specifications Reasonable selection of welding specifications before welding has a significant impact on reducing deformation of the welded part. As the current intensity increases, the deformation of the weldment correspondingly increases. The welding sequence of the weld seam is of great significance in reducing the deformation of the weldment. The structural weld seam should ensure that the weld seam between the two connected components is finally welded. For columnar plate structures, longitudinal (axial) welds should be welded first, followed by circumferential welds. Otherwise, it may cause protrusion deformation or even cracks in the center of the structure. If the weldment is a metal plate composed of some steel plates, the transverse weld of the steel plate shall be welded first. When a single Flat noodles is formed, it can be welded in sections. Each section is welded in the direction opposite to the general direction of welding, that is, the reverse welding method is used. In addition, when welding weldments, if conditions permit, quick and multi-layer welding methods should be used as much as possible. The shorter the interval time between each layer, the better the effect.

The non-destructive testing method that utilizes the principle of electromagnetic induction to non-destructive evaluate certain properties of conductive materials and their workpieces by detecting changes in induced eddy currents within the tested workpiece, or to detect defects, is called non-destructive testing. In industrial production, eddy current testing is one of the main means to control the quality of various metal materials and a few non-metals (such as graphite, carbon fiber composite materials, etc.) and their products. Compared with other non-destructive testing methods, eddy current testing is easier to achieve automation, especially for profiles such as pipes, rods, and wires, which have high testing results. The following introduces the applications of non-destructive testing in some new fields: 1.1 Thickness measurement The application of thickness measurement mainly has two aspects: measurement of the thickness of the film layer on the metal substrate and measurement of the thickness of the metal sheet. The measurement of insulation layer thickness on non-magnetic metals is an important application field of eddy current thickness measurement. Due to the fact that non magnetic metals are all non-ferrous metals with high conductivity, measuring the thickness of their surface insulation layer essentially measures the distance between the probe coil and the base metal. In order to suppress the influence of changes in the conductivity of the substrate metal on the measurement results, a higher detection frequency is generally chosen. At this time, the influence of the substrate conductivity on the inductance component can be ignored, while the influence on the resistance component is still significant. Due to the fact that the inductance component is mainly affected by distance changes. The resistance component is mainly affected by changes in conductivity. Therefore, as long as the inductance of the probe impedance change signal is taken out from the circuit, and then zeroed and corrected, the change in insulation layer thickness can be measured. When the surface of magnetic metal is covered with non-magnetic metal or insulation layer (such as chromium plating or paint layer on steel parts), electromagnetic induction method can also be used to measure its thickness. When the excitation current passes through the coil, a magnetic path is established between the detection coil and the magnetic substrate. Due to changes in the gap between the coil and the magnetic substrate (i.e. the influence of non magnetic film thickness), it will change the magnetic negativity of the magnetic circuit and cause changes in the magnetic flux in the magnetic circuit. Therefore, by measuring the induced voltage on the detection coil, a quantitative relationship curve between the induced voltage and the gap (i.e. film thickness) can be obtained, Then mark it on the dial of the indicating instrument, and the thickness of the film can be directly read from the indicating instrument in the future. When measuring the thickness of metal thin plates using eddy current method, the detection coil can use both reflection method and transmission method. The reflection method refers to the method where the transmitting and receiving coils of the probe are on the same side of the measured body, and the received signal is a signal of impedance amplitude change. The change in material thickness has a non-linear relationship with the impedance change of the receiving coil. Therefore, it is required to achieve nonlinear correction within the measuring instrument, which can result in significant measurement errors. The transmission method is based on the distribution of eddy current field generated by the probe line, that is, the phase lag of eddy current increases with depth at different depths. The thickness value of the tested material is directly obtained based on the phase difference between the received signal and the excitation signal, without the need for nonlinear correction. 1.2 Eddy Current Testing Due to the skin effect of eddy current, eddy current testing can only be used to detect defects on the surface and near surface of metal workpieces. However, due to its advantages of simplicity, no need for coupling agents, and easy implementation of high-speed automatic detection, it has been widely used in the detection of metal materials and components. Eddy current testing can also be used for maintenance and inspection. Due to special working conditions (such as working at high temperature, high pressure, and high speed), certain mechanical products are often prone to fatigue and corrosion cracks during use. Although magnetic particle testing, penetration testing, and other methods are effective for these defects, eddy current testing is not only sensitive to these defects, but can also be used to inspect components coated with coatings such as paint and epoxy resin, as well as blind hole areas and threaded groove bottoms. It also causes cracks in structural components under the skin, which has attracted attention in the maintenance industry. 1.3 Material sorting Eddy current testing is an important factor that affects the coil impedance, as the conductivity and magnetic permeability of the specimen are important factors. Therefore, the material of certain specimens can be evaluated by measuring the changes in conductivity or magnetic permeability of different specimens. The material testing of non-magnetic metal materials is generally carried out through the measurement of electrical conductivity. During testing, the test piece does not need to be further processed, as long as there is a small plane on the surface of the test piece (such as the requirement of 10-20mm for the 7501 eddy current conductivity meter) to place the probe. The detection is simple and feasible, and is suitable for rapid non-destructive inspection of certain properties of metal materials or parts. By measuring the conductivity, it is possible to identify the metal composition and impurity content, the heat treatment status and hardness of metals, and the sorting of mixtures of various metal materials or parts. It can be seen that the conductivity measured by eddy current method provides an effective method for material quality management and inspection. The material testing of ferromagnetic materials is generally carried out through the measurement of magnetic properties. For example, the strong magnetization method utilizes certain quantities in the hysteresis loop of magnetic materials as detection variables. Due to the fact that these quantities (such as saturation magnetic induction strength Bm, residual magnetism Br, coercive force Hc, etc.) are sensitive to the material of the specimen, there may be corresponding relationships between them and the microstructure, heat treatment state, and mechanical properties of the specimen. Therefore, as long as the values of certain variables in the hysteresis loop are detected, the heat treatment status and sorting mix of the material can be inferred based on this corresponding relationship. The weak magnetization method uses the initial magnetic permeability as the detection variable, and can directly use certain eddy current flaw detectors (such as FQR7505) for material sorting. 1.4 Metal surface rust detection When rust occurs on the gold surface, the rust products (mainly metal oxides) have different physical properties from the base metal. The differences in their physical properties, especially between conductivity and magnetic permeability, can affect the reflection resistance and inductance of the eddy current probe coil, making it possible to use eddy current method to detect corrosion on metal surfaces. In order to detect corrosion on metal surfaces, we have developed a dual coil eddy current sensor, which uses experimentally determined detection rate excitation and corresponding detection circuits to detect corrosion on metal surfaces. According to our experiment, the lift off effect curve of the corroded specimen at a fixed frequency is approximately a straight line. The degree of corrosion on the metal surface can be accurately determined from the change in the slope of the straight line. For carbon steel parts, the more severe the surface corrosion, the smaller the slope of the straight line. After using a microcomputer data acquisition system, it is very convenient to complete the collection, conversion, and processing of detection signals. only To move the detection probe up and down above the sample, the lift-off effect curve of the sample can be displayed on the screen. Then, the fitting line can be drawn through linear regression processing, and the fitting line can be drawn through linear regression processing to calculate the slope of the line. Then, compare this slope with the detection results of the standard sample, and those with smaller slope values will have more severe corrosion. As a new non-destructive testing method, eddy current testing technology and theoretical research have made rapid progress. With the development of electronic technology, especially computer and information processing technology, eddy current testing equipment is constantly moving towards microcomputerization and intelligence, and the quantitative evaluation and display technology for defects is constantly improving. It can be foreseen that the application of eddy current testing technology will become increasingly widespread. 1.5 Simulation detection of surface and near surface crack defects in metal For subsurface cracks, as the depth of the defect increases, the time for the maximum induced magnetic field to appear will be longer; However, for surface cracks, the maximum value of the induced magnetic field for cracks of different depths occurs at almost the same time. This indicates that pulsed eddy current is more suitable for quantitative detection of deep subsurface cracks. In practical applications, the corresponding curve between the depth and the time when the maximum value of the induced magnetic field appears can be drawn based on the response data of artificial defects at different depths. After measuring the time when the maximum value of the defect response signal appears in actual testing, the depth of the defect can be determined by corresponding to the reference curve. 1.6 Quantitative detection and scanning imaging of corrosion defects Quantitative detection of corrosion defect length, quantitative detection of corrosion defect depth using the zero crossing time of transient induced voltage signal, and quantitative detection of corrosion defect volume using the peak value of transient induced voltage signal. When using an eddy current array coil with 8 detection coils symmetrically arranged in the center of the bottom of the excitation coil to scan and process samples with simulated corrosion defects, there is a rule between the ratio of the maximum peak value of the eddy current response signal received by the two detection coils at the symmetrical position: for different corrosion depths, when the probe array is completely scanned by corrosion, the ratio is greater than or equal to 0.5; When the probe array is not completely scanned for corrosion, the ratio is less than or equal to 0.2. Therefore, this ratio can be used as a characteristic parameter to determine whether the detection coil has undergone corrosion, for probes that have not undergone corrosion. When displaying a corroded image, the scanning path it passes through will not be displayed. This can effectively eliminate image distortion. 1.7 Actual testing of in-service pipelines and pipelines The China Special Equipment Testing and Research Center applied the InCotest pulse eddy current detector manufactured in the Netherlands to conduct actual testing on the in-service condensate oil pipeline of an oil and gas separation plant and the steam pipeline of a thermal power plant. Without removing the protective layer and insulation layer, two corrosion defects were found when using pulse eddy current technology to inspect the internal pipeline. The measurement results of these two corrosion depths using pulse eddy current method were compared with the ultrasonic measurement results under the conditions of removing the protective layer and insulation material. The maximum errors were 0.69 mm and 0.64 mm, respectively, which can meet the measurement accuracy requirements of engineering inspection standards. New Applications of 1.8 Eddy Current Non destructive Testing Technology in the Steel Industry Eddy current testing, as one of the five conventional non-destructive testing methods, is widely used in the steel industry, including metal rod and wire inspection, fatigue crack detection of structural components, identification of material composition and impurity content, identification of heat treatment status, mixed material sorting, measurement of thickness of metal thin plates, and many other aspects. In recent years, with the deepening of understanding of eddy current testing technology and the development of computers, instruments, and digital signal processing technology, eddy current non-destructive testing technology has made certain breakthroughs in the application of the steel industry. For some problems that were previously considered as detection limits or "impossible", solutions or ideas have been found. For example, some people have proposed online simulation testing of surface defects in high-temperature continuous casting slabs above 1100 ℃, which increases the temperature of traditional eddy current testing objects by several hundred degrees. A Swedish company has developed eddy current testing equipment for detecting 1000 ℃ high-temperature steel and other metal plates and billets. In addition, the application of eddy current detection has also extended to stainless steel capillary tubes, wire with a diameter less than 1mm, and liquid level detection in crystallizers. 1.8.1 Detection of Surface Defects in 1000 ℃ High Temperature Continuous Casting Slabs The limitation of eddy current testing for high-temperature products mainly lies in the temperature that the probe can withstand. Traditional eddy current testing technology can detect temperatures up to 550 ℃ under high temperature conditions. If a water-cooled probe is used for testing, the temperature can still be increased. Jia Huiming and others developed high-temperature eddy current probes using special materials, using a combination of air cooling and water cooling to maintain the internal temperature of the sensor below 40 ℃ and withstand strong high-temperature radiation for a long time. The experiment shows that the high-temperature probe can be used to detect surface defects with a depth of 1.5mm, a width of 0.3mm, and a length of 10mm on the cast slab above 1100 ℃ online. This technology can effectively suppress the noise impact caused by vibration marks on the surface of the casting billet, and with the help of computer signal processing technology, achieve the positioning, quantitative analysis, and printing record of surface defects on the hot casting billet, providing a technical basis for online non-destructive testing of the continuous casting billet. According to information, a Swedish company designed and manufactured a device based on eddy current technology that can inspect surface defects of steel and other metal plates and billets at around 1000 ℃. This device can ensure that both almost vertical directions of the steel surface are scanned. By using an analyzer composed of computers, the input signals can be divided into three main categories: serious defects, harmless defects, and unrecognized defects, and the location of any defects can be identified. This device can accurately determine the position of 0.5mm deep scratches on the surface of the blank. 1.8.2 Detection of stainless steel capillary tubes Although electromagnetic eddy current testing is feasible for offline or online non-destructive testing of extremely small pipe diameters such as stainless steel capillaries, special probes must be configured to achieve satisfactory results. Due to the extremely small diameter of the capillary tube, the current technology level is not yet able to produce an internal penetration probe, nor can point probes be used for detection. Only external penetration probes can be used for detection. The differential external penetration probe jointly developed by Xi'an Jiaotong University and Ederson (Xiamen) Electronics Co., Ltd. is equipped with a specially designed advanced external penetration special probe after calculating and optimizing the width and thickness of the coil, the span between the two coils, the gap between the probe and the capillary, and the wire diameter. At a detection frequency of 666kHz Φ 1mm and Φ A 0.45mm stainless steel capillary tube was used for detection, and good results were achieved. 1.8.3 Online detection of steel wire There are generally two methods used for online detection of steel wires: one is the rotary detection type, where the eddy current detector rotates at high speed around the steel wire. This method is mainly used to detect cracks, scratches, and wire drawing scratches that extend longitudinally along the steel wire. The trajectory of the detector is spiral shaped relative to the movement of the steel wire. Using multiple detectors in parallel for high-speed rotation can achieve 100% inspection, but its sensitivity for surface inspection is limited. It is difficult to maintain a constant distance between the detector and the steel wire. As the gap increases, the sensitivity decreases. If the steel wire is eccentric, the gap will change. The use of high-speed processors can automatically sense gaps and continuously compensate, improving the sensitivity of the system. The other type is the surround coil type. The steel wire passes through the circular coil, and the transducer effectively checks the distribution of eddy currents in one section and compares it with the previous section. It is suitable for detecting point defects and circumferential cracks, and has high sensitivity for transverse cracks, V-shaped cracks, inclusions, pits, and folds. Fast detection speed and wide detection diameter range. The driving current of the surround coil type is higher than that of the rotary detection type, which has better depth penetration. The system has good stability and is not affected by temperature changes and other factors. When the magnetic material is below the Curie point of 800 ℃, magnetic saturation will suppress the signal, but it can be avoided by adjusting the magnetic field strength to improve sensitivity. At present, most of the methods use surround coil, and a combination of the above two methods can also be used. Eddy current technology has been well applied in wire drawing, oil tempering production lines, cold heading steel wire or spring steel wire production. The water-cooled coil is used to detect wire rods with a temperature exceeding 1100 ℃, and its detection speed exceeds 500km/h. 1.8.4 Liquid level detection The precise detection of mold liquid level is the key to achieving automatic liquid level control in the continuous casting production process. The eddy current type liquid steel level gauge has significant advantages such as fast reaction speed, high measurement accuracy, no need for special safety protection, and easy installation and maintenance. Its practicality has made rapid progress. Song Dongfei introduced the use of domestically produced RAM series vortex type liquid steel level controllers in the renovation of Pangang. The measurement system uses an eddy current sensor to measure the liquid level of molten steel. The 50 kHz high-frequency signal generated by the oscillator is supplied to the primary coil (excitation coil) of the sensor. Due to the influence of eddy current in the molten steel, the alternating magnetic field generated by the primary coil changes with the height of the liquid level. A voltage V will be generated within the secondary coil (measuring coil) that varies in direct proportion to the intensity of the magnetic field passing through the coil γ V2, thus the differential voltage (V1-V2) varies with the liquid level height. adopt

The planning for prefabricated buildings has been intensively introduced since 2015. At the end of 2015, the "Evaluation Standards for Industrial Buildings" was issued, and it was decided to comprehensively promote prefabricated buildings nationwide in 2016, achieving breakthrough progress; On November 14, 2015, the Ministry of Housing and Urban Rural Development issued the "Outline for the Modernization of the Construction Industry", which plans to have prefabricated buildings accounting for over 20% of new buildings by 2020 and over 50% of new buildings by 2025. So new requirements have been put forward for testing technology. Ge Yu Technology's technical team has conducted a large number of non-destructive testing experiments (digital DR testing) on various sleeve grouting samples, and obtained the following experience for reference: The reliability of sleeve grouting connection is mainly controlled by two indicators: the length of the steel bar inserted into the sleeve, and the fullness of the grouting. Portable DR testing technology is currently the most intuitive and convenient non-destructive testing technology for the above two indicators, with reliable results. The image is clear, the internal grouting saturation is clear at a glance, and the position of the steel bars is clear.     2. To achieve good detection results, two necessary conditions are required: 2.1 The penetration ability of the X-ray machine should be strong: the 300kV constant pressure portable function of the microfocus can meet the requirements of penetrating 200-300mm concrete.        The software function of the 2.2 DR imaging system needs to be powerful: due to the complex structure of concrete, the attenuation coefficient of rays is different from the general laws of industry and medical treatment, and high-level image processing software is required for noise reduction and sharpening processing. Only then can high-quality images be obtained for observation and accurate conclusions be drawn.         3. Regarding the parallel arrangement of double row sleeves, and the overlap of steel bars and grouting at nodes, as well as the vertical radiographic images of double row grouting sleeves, it has an impact on the identification of internal density; Tilted transillumination images will differentiate.     

双相不锈钢具有奥氏体和铁素体的双相组织，而且单相含量一般都大于30%，兼有奥氏体和铁素体不锈钢的特点，并且在塑性、韧性、耐腐蚀性等方面都“青出于蓝而胜于蓝”。 双相不锈钢焊缝的无损检测 射线检测 目前在海洋石油天然气平台的建造过程中，通常采用传统的射线检测方法检测双相不锈钢焊缝的内部缺陷。射线检测技术比较成熟，在工程项目的应用中属于稳定且保守的检测方法；但射线检测也存在“致命”的缺点——电离辐射，因此射线作业必须在隔离的条件下进行，在周边一定区域内不允许有其他任何施工人员；尤其是管线工作进入安装阶段后，射线检测往往难以实现中心曝光，导致检验效率低下，严重影响项目进度。 超声检测 超声检测也是针对焊缝内部缺陷的传统检测方法之一，并且对坡口未熔合等高危面状缺陷较为敏感。但双相不锈钢焊缝及其邻近区域的晶粒较为粗大，声波能量衰减严重、信噪比差，甚至无法区分缺陷信号和杂波信号；另外，由于超声波检测对检测数据的可记录性差，且受人员技能水平的影响较大，在某种程度上制约了其在双相不锈钢管线焊缝中的应用。 超声相控阵检测 超声相控阵技术是传统超声检测的延伸应用，近年来发展迅速。在海洋工程项目中，超声相控阵检测低合金钢的方法越来越广泛。面对双相不锈钢焊缝的粗大晶粒时，为了提高声束的穿透能力，相控阵利用声束的可控性会生成一定角度范围的纵波。但由于受偏转能力的制约，为了实现焊缝内部和热影响区的声束有效覆盖，必须去除焊缝表面余高，使探头横跨在焊缝上扫查。但去除余高后的焊缝表面粗糙度较大，耦合探头时在声束初始位置(约2~3mm)有较为强烈的耦合信号，此信号可能会掩盖上表面区域的缺陷，存在漏检风险；另外此工艺需要多次扫查，检验效率不高。 Schematic of Clutter Coupling Across Welds Detection process based on TRL probe Detection object The welding seam specification of the inspected pipeline is 450mm in diameter and 14.27mm in wall thickness. The "V" groove argon arc welding method is used, and the material is duplex stainless steel (grade S31803). Section diagram and appearance of the inspected weld seam Characteristics of TRL probe   DMA (short for Dual Matrix Array) is a two-dimensional matrix phased array probe belonging to the TRL (longitudinal wave one transmit one receive) series, which can significantly improve the penetration ability and signal-to-noise ratio of sound beams, mainly due to the following advantages of this probe: 1. Adopting low-frequency longitudinal wave mode 2. Adopting a one send one receive mode 3. The wedge size is small, and the energy loss of sound waves in the wedge is relatively small Appearance of DMA probe wedge Sound beam simulation and detection process The phased array detection area should include the interior of the weld seam, the heat affected zone, and its adjacent areas. To ensure that the sound beam effectively covers the inspected area, it is necessary to simulate the propagation of the sound beam to determine and optimize the ultrasonic phased array detection process. The SetupBuilder acoustic beam simulation software is simple and practical. Based on theoretical acoustic formulas, it guides the setting of detection process parameters by calculating and simulating the beam coverage generated by various types of transducers under specific process settings. nd acoustic beam simulation, taking into account the directionality of incomplete fusion in the groove, the detection process was determined to use DMA probes as the main method for single-sided and double-sided sector scanning, supplemented by low-frequency linear array probes for transverse wave detection. Schematic diagram of DMA probe and linear array probe detection process Process certification   To ensure the reliability of the process, process certification is conducted on the demonstration test block with defects to ensure that all defects in the demonstration test block can be effectively detected, and the size and position of the detection can match the actual situation. Demonstration block structure diagram   In order to simulate the actual state of the inspected weld seam more realistically, the material of the demonstration block is directly cut from the inspected pipeline and welded according to the welding process of the inspected weld seam. In the above figure, A is the surface groove used to simulate surface defects such as weld toe cracks; B is the groove at the groove, used to simulate surface defects such as incomplete fusion in the internal groove of the weld seam; C is the root groove used to simulate defects at the root; D is the internal hole of the weld seam, used to simulate volumetric defects such as pores and slag inclusions inside the weld seam. The experiment uses the Olympus OMNISCAN MX2 ultrasonic phased array detector, which sequentially calibrates the sound speed, wedge delay, angle calibration gain, and TCG (depth compensation) curve. Suitable encoders and scanning frames are installed, and the scanning process is followed to scan and save the data. The results show that the detection process can effectively detect all defects in the test block, and the positioning and quantitative results are basically consistent with the actual values, indicating that the process is feasible within the allowable error range. Demonstration block ultrasonic phased array detection effect diagram Field application   During the application of ultrasonic phased array testing technology to replace traditional radiographic testing in a liquefied natural gas (LNG) pipeline, a defect of approximately 50mm in length was found at the root of a certain weld seam. On site phased array detection results   During the removal of the pipeline near the welding junction, it was visually observed that one side of the root was not fused, and its length was measured to be approximately 48mm. Actual appearance of defects   The visual results and phased array detection results are almost identical, further verifying the effectiveness and reliability of the process.   Conclusion: The detection process based on DMA probes can effectively detect duplex stainless steel welds and effectively solve the shortcomings of traditional detection methods and processes. In multiple ocean engineering projects, using this testing process as a substitute for radiographic testing can make significant contributions to project progress while ensuring engineering quality, and has significant application value.